I know it may sound like I am beating a dead horse but are you using Smart Action, and how often are you able to turn off your mobile data and 4g? I typically have 4 to 5 hours of display time, I stream music and have NFL Access on for my commute. Talk times are usually 1 to 2 hours. What saves me the only time 4g is on is during my 50 minutes of commute time each day, but when I am at home or work it turns off using Smart Actions. Learning how to use that function will double your battery life if you are lucky like me and have good WIFI connection at work and home.
Edit: I was getting 21 to 28 hours before I set up SA.